The invention relates to the field of plastic articles.
Polyethylene terephthalate (also referred to as “PET”) is a polyester of terephthalic acid and ethylene glycol that can be obtained by the polycondensation of dimethyl terephthalate with ethylene glycol, and also terephthalic acid with ethylene glycol or ethylene oxide. PET exists both as an amorphous (transparent) and as a semi-crystalline (opaque and white) thermoplastic material. Generally, it has useful chemical resistance to mineral oils, solvents and acids but not to bases. Semi-crystalline PET has good strength, ductility, stiffness and hardness. Amorphous PET has better ductility but less stiffness and hardness. PET is used to make bottles for soft drinks and other household and consumer products. Generally, PET has many uses and several large markets. For this reason, the volume of PET manufactured is large and growing.
Unfortunately, despite recycling efforts, billions of pounds of PET are still dumped into landfills annually all over the world. Other PET that is not reused is incinerated. The PET that is disposed into landfills creates significant waste. The incineration of PET also wastes a significant resource that could be used more effectively.
Articles made from thermoplastic molding compositions based on polybutylene terephthalate (also referred to as “PBT”) and PBT in combination with other materials are used in various applications. Although conventional articles derived from PBT molding compositions are useful to many customers, conventional PBT-molding compositions generally cannot be made from recycle sources of PBT due to the lack of availability of large post-consumer or post-industrial PBT. PET, unlike PBT, is made in much larger quantities and is more easily recovered from consumer wastes. If PET (scrap) materials could be converted to PBT and converted into useful molding compositions, then there would exist a valuable way to effectively increase the use of scrap PET in PBT thermoplastic molding compositions and articles therefrom. If PET (scrap) materials could be converted to PBT and into useful molding compositions, then there would be an effective way to use of post consumer or post-industrial streams in PBT applications and articles. PBT made this way would conserve non-renewable hydrocarbon resources and reduce the formation of greenhouse gases, e.g., CO2.
U.S. Pat. No. 5,451,611 teaches a process for converting waste poly(ethylene terephthalate) to either poly(ethylene-co-butylene terephthalate) or poly(butylene terephthalate) (PBT) by reaction with 1,4-butanediol. In discussing the prior art, U.S. Pat. No. 5,451,611 indicates that in most of the processes it cites, the undesirable byproduct diethylene glycol is formed which contaminates the final product and has to be removed by purification before the recovered products can be reused again. A principal object of U.S. Pat. No. 5,451,611 was to provide a process for converting poly(ethylene terephthalate) waste directly to another high value polymer without breaking down the poly(ethylene terephthalate) to its constituent monomers or oligomers. The patent discloses numerous examples in which a variety of polymers have a diol incorporated at various amounts. Example 11 shows a PBT polymer being formed with a complete replacement of ethylene glycol with 1,4-butanediol.
U.S. Pat. No. 5,266,601 teaches a process for making “PBT” from PET by reacting PET with 1,4-butanediol. A principal object of U.S. Pat. No. 5,266,601 was to produce PBT containing less than 1.0 wt % units of ethylene glycol from PET scrap. Another principal objective of U.S. Pat. No. 5,266,601 was to develop a process that facilitates the reduction of THF generated in the process as much as possible to the extent that this PBT is economically competitive with PBT obtained from monomers. U.S. Pat. No. 5,266,601 emphasizes the production of PBT having ethylene glycol groups in an amount that is less than 1 wt %. In the instances where compositions contain more than 1 wt %, U.S. Pat. No. 5,266,601 presents these compositions in comparative examples. Such compositions are described as having “yellowish” and “slightly yellowish” colors, respectively.
Japanese laid-open application 2005-89572 teaches a method for producing polybutylene terephthalate by transesterifying bis(2-hydroxyethyl) terephthalate with 1,4-butanediol in the presence of a transesterification reaction catalyst under the pressure of 1-54 kPa at a final temperature ranging from 200-230° C. and then subjecting the reaction product to polycondensation. In one embodiment, the bis(2-hydroxyethyl)terephthalate is obtained by depolymerizing polyethylene terephthalate with excessive ethylene glycol, and purifying the depolymerized product. The patent teaches that transesterifying bis(2-hydroxyethyl) terephthalate with 1,4-butanediol under reduced pressure imparts favorable results.
Although such documents disclose ways of using PET scrap, such documents do not meet the long felt need of using PET scrap that is ordinarily incinerated or buried in landfills in molding compositions or articles made from molding compositions. U.S. Pat. No. 5,451,611, for instance, does not teach effective processes that enable PET to be able to be broken down into its constituent monomers or oligomers—a feature that is sometimes required by commercial considerations. U.S. Pat. No. 5,451,611 does not provide meaningful guidelines for making compositions functionally similar to PBT containing ethylene glycol in amounts other than trace amounts and which exhibit melting temperatures that are higher than those shown in its examples. Similarly, U.S. Pat. No. 5,266,601 does not provide meaningful details about how to make molding compositions containing fillers, other materials such as flame retardants, impact modifiers, epoxies, polyester resins such as PET, polytrimethylene terephthalate and polycarbonates, and PBT with a PET residue such as ethylene glycol in any amount, let alone an amount that is more than 1 wt %. In fact, neither patent discusses if or how the materials they describe can be used in molding compositions containing fillers and other materials such as flame retardants, impact modifiers, epoxies, polyesters and polycarbonates. Japanese laid-open application 2005-89572 is also silent about PBT molding compositions as well as methods for utilizing PET effectively to make such compositions.
Known technology relating to utilizing PET as scrap materials for making PBT-like materials does not provide meaningful solutions that solve the long felt need to increase the use of PET scrap that is ordinarily incinerated or buried in landfills. Known technology does not provide meaningful solutions that solve the long felt need for PBT thermoplastic compositions from PBT derived from PET that exhibit a combination of physical properties that are highly useful in compositions and articles that are valued by customers.
For the foregoing reasons, there is a need to develop new articles made from molding compositions that utilize PBT derived from post consumer and post industrial PET and that have useful performance properties.
For the foregoing reasons, there is a need to develop new articles made from molding compositions that reduce the usage of non-renewable hydrocarbon resources and the amount of CO2 emissions generated per unit of PBT.
For the foregoing reasons, there is a need to develop new processes for making articles from molding compositions that utilize PBT derived from PET and that have useful performance properties.